1. Field of the invention
The present invention relates to an inflatable passive restraint system for use in a vehicle. Such systems, generally referred to as airbag systems, are widely used in modern automobiles and trucks. The present invention is directed to an inflatable cushion assembly which is designed to deploy in front of and engage the knee area of a vehicle's occupant in the event of a collision.
2. Description of related art
Airbag systems are recognized as being effective in protecting vehicle occupants in the event of a collision. These systems have been primarily designed to deploy in front of an occupant's torso, and particularly between the upper torso and the vehicle's windshield and instrument panel. They are effective in restraining the occupant's upper body, preventing the occupant from striking the instrument panel or the windshield in a sudden deceleration such as occurs in a collision.
During a front end collision there is a tendency for an occupant, particularly one who is not properly restrained by a seat belt, to slide forward along the seat and "submarine" under the primary airbag. To prevent such an occurrence some vehicles have provided a fixed crushable panel, referred to as a knee bolster, extending downwardly and toward the occupant's knee or lower leg from the instrument panel. During a collision the occupant's legs slide forward and contact the bolster stopping the occupant from sliding further forward under the primary airbag. This panel, however, is fairly large and when optimally located relatively close to the occupant's legs, greatly diminishes the amount of leg room available in front of the occupant.
Other systems, as illustrated in U.S. Pat. Nos. 3,618,977, 3,618,978 and 3,768,830, have used primary airbags which deploy from a relatively low portion of the instrument panel and contact the occupant's leg or knee area as they expand into the area between the occupant's upper torso and the instrument panel and windshield. Another proposal, illustrated in U.S. Pat. No. 4,948,168, uses forces applied by the deploying primary airbag to move or rotate a bolster panel into position in front of the occupant's legs or knees. These systems require very large primary airbags, which are difficult to deploy in the required short activation time, and, in any event, require large inflators. This is a detriment to vehicle manufacturers who generally seek to minimize the space and weight requirements of the components used in their vehicles.
Further systems have been disclosed, in U.S. Pat. Nos. 3,817,553 and 5,458,366, for example, which provide a separate airbag for the knee bolster. The airbag can either directly contact the leg or knee or, as illustrated in several embodiments of the 3,817,553 patent, can provide the motive force for deploying padded deformation members to a position against the occupant's knee. These systems, as illustrated, require substantial space at the surface of the instrument panel and directly behind such surface. Such not only precludes the use of such space for other components, it essentially requires that the knee bolster assembly be specifically and individually designed for each instrument panel design in which it is used. Moreover, the systems incorporate many parts into their assemblies, which not only reduces their overall reliability, it makes them relatively expensive to produce.